Author(s):
Knaapila, M. 
; Dias, F. B. ; Garamus, V. M. ; Almásy, L. ; Torkkeli, M. ; Leppänen, K. ; Galbrecht, F. ; Preis, E. ; Burrows, H. D. ; Scherf, U. ; Monkman, A. P.
Date: 2007
Persistent ID: http://hdl.handle.net/10316/10455
Origin: Estudo Geral - Universidade de Coimbra
Description
We report on the phase behavior of poly(9,9-dihexylfluorene) (PF6), poly(9,9-diheptylfluorene) (PF7), poly(9,9-dioctylfluorene) (PF8), poly(9,9-dinonylfluorene) (PF9), and poly(9,9-didecylfluorene) (PF10) in methylcyclohexane (MCH). After a heating−cooling cycle, in the 10−50 mg/mL concentration range, PF6/MCH, PF7/MCH, PF8/MCH, and PF9/MCH systems were found to be gel-like, while PF10/MCH appears less viscous. PF6/MCH, PF7/MCH, PF8/MCH, and PF9/MCH form large (10−100 nm) sheetlike assemblies (thickness of 2−3 nm). The larger length scale structures of these sheets show an odd−even dependence on the side chain (spacer) length: the PF6 and PF8 sheets are broader and thinner, whereas PF7 and PF9 sheets are thicker with a putative double layer structure. PF10 does not follow this sequence, and only part of the polymer is assembled into a sheetlike structure, the rest remaining dissolved at the molecular level. PF8/MCH and PF9/MCH mixtures also have lower length scale crystalline structures with an internal period corresponding to the periodicity observed in the solid-state β phase of PF8. Vestiges of crystalline domains are found for PF6 and PF7 but not for PF10. PF7/MCH, PF8/MCH, and PF9/MCH systems contain the conformational isomer Cβ, of those chains observed in the β phase, while this is not observed with other polymer/MCH systems. http://dx.doi.org/10.1021/ma0715728
